In response to the development of compact and light weight electronic information products, the semiconductor manufacturing process is now aimed to enable high-density and automated production. On the other hand, the currently available electronic information products or devices are designed to have a touch sensing surface or touchscreen that is gradually increased in size. As a result, the conductive electrodes for the touchscreen originally made of an indium tin oxide (ITO) material are now replaced by metal conductive electrodes.
Please refer to FIGS. 1 and 2 that show the manufacturing process and the structure of conventional metal conductive electrodes 10. In a first step, a metal conductive electrode layer for forming the main bodies of the metal conductive electrodes 10 is adhered to a substrate 12 via at least one adhesion layer 11, which is also referred to as a bonding layer, so that the metal conductive electrodes 10 formed later do not easily separate from the substrate 12. In a second step, at least one weatherproof layer 13, which is also referred as an anti-corrosion layer, is covered on the metal conductive electrode layer.
Please refer to FIG. 3, the adhesion layer 11 for the conventional metal conductive electrodes 10 includes two sublayers, namely, an intermediate layer 110 connected to the substrate 12 and an electrically conductive seed layer 111 connected to the metal conductive electrodes 10.
In a third step as shown in FIG. 1, a wet etching process using an etching fluid is conducted, so that the weatherproof layer 13, the metal conductive electrode layer for forming metal conductive electrodes 10, and the adhesion layer 11 are etched to form an electrode circuit 14 consisting of a plurality of metal conductive electrodes 10. Finally, after a sensor with the metal conductive electrodes is obtained, the entire surface of the electrode circuit 14 is covered with an optically clear adhesive (OCA) film 16 to protect the sensor against damage.
To avoid the metal conductive electrodes 10 formed on a substrate of the touchscreen from being visually perceived by a user, it is a target of the research and development engineers in the touchscreen industry to develop metal conductive electrodes 10 having a very small width.
More specifically, the electrode circuit 14 on the conventional sensor is protected by the etch-resistant weatherproof layer 13 and is formed through the wet etching process. The wet etching is isotropic. Since the weatherproof layer 13 is formed of an etch-resistant material, there is a relatively large difference between the etching rates of the etching fluid on the weatherproof layer 13 and on the metal conductive electrode layer for forming the metal conductive electrodes 10. Moreover, the weatherproof layer 13 formed in the second step usually has a non-uniform thickness. As a result, when the etching fluid vertically etches the weatherproof layer 13, the metal conductive electrode layer and the adhesion layer 11, a serious side etching 15 will occur on the metal conductive electrodes 10 during the wet etching process.
In other words, when being viewed sidewardly as shown FIG. 1, the side etching 15 tends to occur on the lateral surfaces of the metal conductive electrodes 10 so formed, particularly when the metal conductive electrodes 10 have a designed width smaller than 5 μm and a designed thickness larger than 0.3 μm. As a result, the total etched surface on each of the metal conductive electrodes 10 is too large in proportion to the total area thereof, and the metal conductive electrodes 10 are unevenly etched to result in increased electric impedance of the electrode circuit 14. In some worse conditions, the electrode circuit 14 formed of the metal conductive electrodes 10 will break locally. Therefore, the metal conductive electrodes 10 are not easily controllable in quality and have low yield rate to form a tough problem in manufacturing very fine conductive electrodes.
In view of the disadvantages of the conventional metal conductive electrodes 10 for touchscreen, it is tried by the inventor to develop an improved conductive electrode structure, so that conductive electrodes thereof are not easily visually perceived by a user and do not have the problem of forming an electrode circuit with non-uniform width due to side etching, enabling increased yield rate of the conductive electrode structure.